<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>js引入</title>
    <script src="01js.js"/>
    <script>
        console.log('js写在head标签内部')
    </script>
</head>
<body>
    <!--
    1：写在head标签内部
    alert:弹窗 体验不友好 建议使用console.log()控制台输出
    -->
<script>
    console.log('js写在body标签结束之前')
</script>
</body>
</html>
<script>
    console.log('js写在html结束标签之后')
</script>